JavaScript substr

Returns part of a string

function substr (str, start, len) {
    // Returns part of a string  
    // 
    // version: 909.322
    // discuss at: http://phpjs.org/functions/substr    // +     original by: Martijn Wieringa
    // +     bugfixed by: T.Wild
    // +      tweaked by: Onno Marsman
    // +      revised by: Theriault
    // *       example 1: substr('abcdef', 0, -1);    // *       returns 1: 'abcde'
    // *       example 2: substr(2, 0, -6);
    // *       returns 2: false
// Add: (?) Use unicode.semantics and/or unicode.runtime_encoding (e.g., with string wrapped in "binary" or "Binary" class) to
// allow access of binary (see file_get_contents()) by: charCodeAt(x) & 0xFF (see https://developer.mozilla.org/En/Using_XMLHttpRequest )// Fix: Handle 4-byte characters
 
    str += '';
    var end = str.length;
    if (start < 0) {        start += end;
    }
    end = typeof len === 'undefined' ? end : (len < 0 ? len + end : len + start);
    // PHP returns false if start does not fall within the string.
    // PHP returns false if the calculated end comes before the calculated start.    // PHP returns an empty string if start and end are the same.
    // Otherwise, PHP returns the portion of the string from start to end.
    return start >= str.length || start < 0 || start > end ? !1 : str.slice(start, end);
}

external links: original PHP docs | raw js source

Examples

» Example 1

Running

1	substr('abcdef', 0, -1);

Should return

'abcde'

» Example 2

Running

1	substr(2, 0, -6);

Should return

false

Dependencies

No dependencies, you can use this function standalone.

Open syntax issues

php.js uses JsLint to help us keep our code consistent and prevent some common bugs.

Eventually we want all code to pass or at least take into consideration most fixes suggested by JsLint, following this JsLint configuration we’ve decided on.

Authors

Thanks to the following developers, you get to have substr goodness in JavaScript.

Martijn Wieringa ( original )
T.Wild ( bugfixed )
Onno Marsman ( tweaked )
Theriault ( revised )

Comments

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Use:

[CODE]
your_stuff('here');
[/CODE]

for proper code formatting
By submitting code here you are allowing us to use it in php.js hence dual licensing it under the MIT and GPL licenses

Kevin van Zonneveld
5 Sep '08

@ T.Wild: Sure does, thank you for your bugfix. I've also added a testcase for this situation so it cannot happen again.

T.Wild
3 Sep '08

Had a bit of difficulty when this function was passed an integer instead of a string since

1	.substring

isn't an integer function.

I fixed the error thusly:

1	return (""+f_string).substring(f_start, f_length);

instead of:

1	return f_string.substring(f_start, f_length);

forcing f_string to be a string, since this is how the PHP version treats the first parameter.
[CODE="php"]
substr(1234,2,1) = 3;
[/CODE]

hope this helps.

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